Protesters who used the Brooklyn Bridge walkway were not arrested,” said the head police spokesman, Paul J. Browne. “Those who took over the Brooklyn-bound roadway, and impeded vehicle traffic, were arrested.”

But many protesters said that they thought the police had tricked and trapped them, allowing them onto the bridge and even escorting them across, only to surround them in orange netting after hundreds of them had entered.

Earlier in the afternoon, 10 buses from the Department of Corrections at Rikers Island were dispatched to the site.